Studies will be directed toward the in-vitro cultivation of Treponema pallidum and the comparative lipid composition and lipid metabolism of T. pallidum and the cultivated treponemal species. The use of fatty acids and phospholipids by treponemes will be studied. The mechanism of a commensal culture system involving two different species of treponemes with similar lipid composition to that of T. pallidum will be investigated in order to characterize and identify the growth stimulating compounds. The ability of T. pallidum to grow in this culture system will also be investigated. All information of lipid studies will be applied to experiments designed to grow T. pallidum.